On (03/30/16 08:59), Minchan Kim wrote:
> On Tue, Mar 29, 2016 at 03:02:57PM -0700, Yu Zhao wrote:
> > zs_destroy_pool() might sleep so it shouldn't be used in zpool
> > destroy callback which can be invoked in softirq context when
> > zsmalloc is configured to work with zswap.
>
> I think it's a limitation of zswap design, not zsmalloc.
> Could you handle it in zswap?
agree. hm, looking at this backtrace
> [<ffffffffaea0224b>] mutex_lock+0x1b/0x2f
> [<ffffffffaebca4f0>] kmem_cache_destroy+0x50/0x130
> [<ffffffffaec10405>] zs_destroy_pool+0x85/0xe0
> [<ffffffffaec1046e>] zs_zpool_destroy+0xe/0x10
> [<ffffffffaec101a4>] zpool_destroy_pool+0x54/0x70
> [<ffffffffaebedac2>] __zswap_pool_release+0x62/0x90
> [<ffffffffaeb1037e>] rcu_process_callbacks+0x22e/0x640
> [<ffffffffaeb15a3e>] ? run_timer_softirq+0x3e/0x280
> [<ffffffffaeabe13b>] __do_softirq+0xcb/0x250
> [<ffffffffaeabe4dc>] irq_exit+0x9c/0xb0
> [<ffffffffaea03e7a>] smp_apic_timer_interrupt+0x6a/0x80
> [<ffffffffaf0a394f>] apic_timer_interrupt+0x7f/0x90
it also can hit the following path
rcu_process_callbacks()
__zswap_pool_release()
zswap_pool_destroy()
zswap_cpu_comp_destroy()
cpu_notifier_register_begin()
mutex_lock(&cpu_add_remove_lock); <<<
can't it?
-ss
